May i know what are the matcap colors
Matcap stands for Material Capture. 

In short: They are fake materials which are intended to help you during the modeling process. 

Sometimes using a Matcap instead of the solid shading material in the viewport helps you to spot irregularities in your geometry. If you choose a Matcap similar to the material you have in mind for your final render, it might also help to check if a model will "work" visually. 



See how the edges and creases show up more prominent when using the matcap?

You can't use them as a final material for your renderings, though.